An interchangeable lens type of digital camera is a known imaging device (see Patent Literature 1, for example. The camera discussed in Patent Literature 1 has a lens unit and a camera body. This camera body has a CCD (charge coupled device) image sensor or other such imaging element, and a mirror box disposed between the lens unit and the imaging element. The mirror box apparatus guides light that has passed through the lens unit to either a CCD image sensor or a prism. Light guided to the prism is guided by that prism to a viewfinder.